In a motor for use in an air conditioner and the like, a connection state of coils of the motor is switched between a Y connection (star connection) and a delta connection (also referred to as a Δ connection) in order to enhance operation efficiency during low-speed rotation and during high-speed rotation (see, for example, Patent Reference 1).
Specifically, control is performed in such a manner that a rotation speed of the motor is compared to a threshold, and switching from the Y connection to the delta connection is performed when a state in which the rotation speed is higher than or lower than a threshold continues for a certain time period (see, for example, Patent Reference 2).